1. Field of the Invention
The present invention relates to an ink jet printer, and, more particularly, to a method of ink level determination for multiple ink chambers.
2. Description of the Related Art
An ink jet printer forms an image on a print media sheet by ejecting ink from a plurality of ink jetting nozzles of an ink jet printhead to form a pattern of ink dots on the print media sheet. Such an ink jet printer may include a reciprocating printhead carrier that transports multiple ink jet printheads across the print media sheet along a bi-directional scanning path defining a print zone of the printer. Typically, a mid-frame provides media support at or near the print zone. A sheet feeding mechanism is used to incrementally advance the print media sheet in a sheet feed direction, also commonly referred to as a sub-scan direction or vertical direction, through the printer.
It is known to provide a unitary printhead cartridge that includes both a printhead and a local supply of ink. Such a printhead cartridge may include a multi-chambered ink reservoir for carrying multiple colors of ink, each chamber including a separate supply of ink of a particular color. In one printing system, for example, it is known to include cyan, magenta and yellow inks in such a multi-chambered ink reservoir.
Also, it is known to determine the amount of ink that remains in each of the chambers of a multi-chambered ink reservoir by measuring the ink levels in each chamber. Such a method, however, requires an ink level sensor of some type in each ink chamber. For example, a three-chambered ink reservoir would require three separate ink level sensors to determine the ink levels in each of the three ink chambers.
Further, it is known to estimate the amount of ink remaining in each ink chamber of a multi-chambered ink reservoir. For example, when a printhead cartridge is new, an assumed total ink volume of each color of ink is established. Then, for a particular color, the number of ink drops of that color expelled from the respective ink chamber is counted. The ink volume associated with the ink drop count is then determined, and is subtracted from the assumed total ink volume to arrive at an estimated current ink volume for the respective ink chamber. Such a basic ink level estimation method, however, does not account for extrinsic factors, such as for example, variations in drop volume due to temperature changes and/or ink loss due to evaporation.
What is needed in the art is a method of ink level determination for multiple ink chambers that does not require measuring ink levels in each chamber, and which is more accurate than a basic ink level estimation method.